Purpose: To report potentially distinguishing characteristics between bacterial endophthalmitis and presumed noninfectious endophthalmitis associated with intravitreal triamcinolone acetonide injection., Methods: Records of two patients with culture-proven bacterial endophthalmitis and six patients with presumed noninfectious endophthalmitis from intravitreal triamcinolone acetonide injections were analyzed retrospectively., Results: Two eyes in two patients with culture-proven bacterial endophthalmitis had decreased vision and hypopyon or vitritis, but no pain or conjunctival injection 2 weeks after intravitreal triamcinolone acetonide injection. Seven eyes in six patients with presumed noninfectious endophthalmitis had blurred vision, hypopyon, and variable pain all within 2 days of intravitreal triamcinolone injection. All seven eyes were followed up closely and had rapid resolution of hypopyon and symptoms., Conclusion: Bacterial endophthalmitis after intravitreal triamcinolone acetonide injection may present in an atypical, relatively delayed manner with decreased vision but no pain or redness. Presumed noninfectious endophthalmitis presents within 2 days after the injection, may be accompanied by discomfort, and has a hypopyon that may be the triamcinolone material itself or a sterile inflammatory reaction. In these eyes, the hypopyon and symptoms quickly resolve without treatment.